FreeSewing does not use sizes. All our patterns are drafted to a set of measurements.
Since version 2.2 however, we do provide standard sizes. Each size is a set of measurements that is an estimation of what a person with a given neck circumference could have as measurements.
This is not an exact science. We provide these sizes as a fast and easy way to get started with our patterns. But we do hope that you will take the time to take your own measurements, or have them taken. This will always yield better results.
These tables take up a lot or screen real-estate, which is why we show sizes in a wide view.